1. Field of the Invention
This invention relates in general to magnetic read transducers, and more particularly to a method for forming a read transducer by ion milling and chemical mechanical polishing to eliminate nonuniformity near the MR sensor.
2. Description of Related Art
The heart of a computer is an assembly that is referred to as a magnetic disk drive. The disk drive includes a rotating magnetic disk, write and read heads that are suspended by a suspension arm above the rotating disk and an actuator that swings the suspension arm to place the read and write heads over selected circular tracks on the rotating disk. The read and write heads are directly mounted on a slider that has an air bearing surface (ABS). The suspension arm biases the slider into contact with the surface of the disk when the disk is not rotating but, when the disk rotates, air is swirled by the rotating disk adjacent the ABS to cause the slider to ride on an air bearing a slight distance from the surface of the rotating disk. The write and read heads are employed for writing magnetic impressions to and reading magnetic impressions from the rotating disk. The read and write heads are connected to processing circuitry that operates according to a computer program to implement the writing and reading functions.
The write head includes a coil layer embedded in first, second and third insulation layers (insulation stack), the insulation stack being sandwiched between first and second pole piece layers. A write gap layer between the first and second pole piece layers forms a magnetic gap at an air bearing surface (ABS) of the write head. The pole piece layers are connected at a back gap. Current conducted to the coil layer induces a magnetic field across the magnetic gap between the pole pieces. This field fringes across the magnetic gap for the purpose of writing information in tracks on moving media, such as the circular tracks on the aforementioned rotating disk, or a linearly moving magnetic tape in a tape drive.
The read head includes first and second shield layers, first and second gap layers, a read sensor and first and second lead layers that are connected to the read sensor for conducting a sense current through the read sensor. The first and second gap layers are located between the first and second shield layers and the read sensor and the first and second lead layers are located between the first and second gap layers. The distance between the first and second shield layers determines the linear read density of the read head. The read sensor has first and second side edges that define a track width of the read head. The product of the linear density and the track density equals the real density of the read head, which is the bit reading capability of the read head per square inch of the magnetic media.
Rows and columns of combined read and write heads are made on a wafer substrate located in various chambers where layers are deposited and then defined by subtractive processes. A plurality of substrate wafers may be located on a turntable which rotates within the chamber and which may function as an anode. One or more targets, which comprise materials that are to be deposited on the wafer substrates, may also be located in the chamber. The target functions as a cathode and a DC or RF bias may be applied to the cathode and/or the anode. The chamber contains a gas, typically argon (Ar), which is under a predetermined pressure. Material is then sputtered from a target onto the wafer substrates forming a layer of the desired material. Layers may also be deposited by ion beam deposition wherein an ion beam gun directs ionized atoms (ions) onto a target, which causes the target to sputter material on the wafer substrate. A subtractive process may employ a gas in the chamber, such as argon (Ar), under pressure, which causes sputtering of the material from portions of the wafer substrate not covered by a mask. Alternatively, the subtractive process may employ an ion beam gun that discharges high velocity ions, such as argon (Ar) ions, which impact and remove portions of the wafer substrate that are not covered by a mask.
First and second hard bias and lead layers are typically joined at first and second side edges of the read sensor in what is known in the art as a contiguous junction. A first step in making this junction is forming a read sensor material layer over the entire wafer. Then, for each magnetic head a photoresist is formed over the desired read sensor site with first and second side edges defining the first and second side edges of the read sensor. A subtractive process, such as ion milling, is employed for removing the entire read sensor material layer except the read sensor under the photoresist. While the photoresist is still in place a hard bias and lead layer material is deposited on the entire wafer substrate. The photoresist is then removed lifting off the bias and lead layer material deposited thereon. The result is that a hard bias and lead layer makes good abutting engagement with the first side edge of the read sensor. However, because the hard bias layer is deposited with a resist structure, the layer near the edges of the sensor layer has a nonuniform thickness.
It can be seen that there is a need for a method for forming a read transducer by ion milling and chemical mechanical polishing to eliminate nonuniformity near the MR sensor.